Page 63 - Rangatira Angus Catalogue 2021 ebook

NZ ANGUS BREEDPLAN CE % Direct = Direct Calving Ease - The EBV for direct calving ease indicates
Understanding the EBVs, Selection Indices and Accuracy the influence of the sire on calving ease in purebred females calving at two years
of age.
EBVs CE % Daughters = Daughters’ Calving Ease - The EBV for daughters’ calving
An animal’s breeding value is its genetic merit, half of which will be passed on to its ease indicates how easily that sire’s daughters will calve at two years of age.
progeny. While we will never know the exact breeding value, for performance traits it
is possible to make good estimates. These estimates are called Estimated Breeding Gestation Length EBV (days) is an estimate of the time from conception to the birth
Values (EBVs). of the calf and is based on AI and hand mating records. Lower (negative) GL EBVs
indicate shorter gestation length and therefore easier calving and increased growth after
In the calculation of EBVs, the performance of individual animals within a contemporary birth.
group is directly compared to the average of other animals in that group. A
contemporary group consists of animals of the same sex and age class within a herd, Birth Weight EBV (kg) is based on the measured birth weight of progeny, adjusted for
run under the same management conditions and treated equally. Indirect comparisons dam age. The lower the value, the lighter the calf at birth and the lower the likelihood of
are made between animals reared in different contemporary groups, through the use of a difficult birth. This is particularly important when selecting sires for use over heifers.
pedigree links between the groups. 200-Day Growth EBV (kg) is calculated from the weight of progeny taken between 80
EBVs are expressed in the units of measurement for each particular trait. They are and 300 days of age. Values are adjusted to 200 days and for age of dam. This EBV is
shown as + ive or - ive differences between an individual animal’s genetics difference the best single estimate of an animal’s genetic merit for growth to early ages.
and the genetic base to which the animal is compared. For example, a bull with an EBV 400-Day Weight EBV (kg) is calculated from the weight of progeny taken between 301
of +50 kg for 600-Day Weight is estimated to have genetic merit 50 kg above the breed and 500 days of age, adjusted to 400 days and for age of dam. This EBV is the best
base of 0 kg. Since the breed base is set to an historical benchmark, the average EBVs single estimate of an animal’s genetic merit for yearling weight.
of animals in each year drop has changed over time as a result of genetic progress 600-Day Weight EBV (kg) is calculated from the weight of progeny taken between 501
within the breed.
and 900 days of age, adjusted to 600 days and for age of dam. This EBV is the best
The absolute value of any EBV is not critical, but rather the differences in EBVs between single estimate of an animal’s genetic merit for growth beyond yearling age.
animals. Particular animals should be viewed as being “above or below breed average” Mature Cow Weight EBV (kg) is based on the cow weight when the calf is weighed for
for a particular trait.
weaning, adjusted to 5 years of age. This EBV is an estimate of the genetic difference
Whilst EBVs provide the best basis for the comparison of the genetic merit of animals in cow weight at 5 years of age and is an indicator of growth at later ages and potential
reared in different environments and management conditions, they can only be used feed maintenance requirements of the females in the breeding herd. Steer breeders
to compare animals analysed within the same analysis. Consequently, NZ ANGUS wishing to grow animals out to a larger weight may also use the Mature Cow Weight
BREEDPLAN EBVs cannot be validly compared with EBVs for any other breed. EBV.
Although EBVs provide an estimate of an animal’s genetic merit for a range of production Milk EBV (kg) is an estimate of an animal’s milking ability. For sires, this EBV indicates
traits, they do not provide information for all of the traits that must be considered during the effect of the daughter’s milking ability, inherited from the sire, on the 200-day weights
selection of functional animals. In all situations, EBVs should be used in conjunction of her calves. For dams, it indicates her milking ability.
with visual assessment for other traits of importance (such as structural soundness, Scrotal Size EBV (cm) is calculated from the circumference of the scrotum taken
temperament, fertility etc). A recommended practice is to firstly select breeding stock between 300 and 700 days of age and adjusted to 400 days of age. This EBV is an
based on EBVs and to then select from this group to ensure that the final selections are estimate of an animal’s genetic merit for scrotal size. There is also a small negative
otherwise acceptable. correlation with age of puberty in female progeny and therefore selection for increased
EBVs are published for a range of traits covering fertility, calving ease, milking ability, scrotal size will result in reduced age at calving of female progeny.
growth, carcase merit and feed efficiency. When using EBVs to assist in selection Days to Calving EBV (days) indicates the fertility of the daughters of the sire. It is the
decisions it is important to achieve a balance between the different groups of traits and time interval between the day when the female is first exposed to a bull in a paddock
to place emphasis on those traits that are important to the particular herd, markets and mating to the day when she subsequently calves. A negative EBV for days to calving
environment. One of the advantages of having a comprehensive range of EBVs is that indicates a shorter interval from bull-in date to calving and therefore higher fertility.
it is possible to avoid extremes in particular traits and select for animals with balanced
overall performance. Carcase Weight EBV (kg) is based on abattoir carcase records and is an indicator of
the genetic differences in carcase weight at the standard age of 750 days.
Calving Ease EBVs (%) are based on calving difficulty scores, birth weights and
gestation length information. More positive EBVs are favourable and indicate easier Eye Muscle Area EBV (sq cm) is calculated from measurements from live animal
calving. ultrasound scans and from abattoir carcase data, adjusted to a standard 400 kg carcase.
This EBV estimates genetic differences in eye muscle area at the 12/13th rib site of a
400 kg dressed carcase. More positive EBVs indicate better muscling on animals. Sires
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